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When you first get into backpacking, one of your main investments will be your backpack. Once you start shopping around for a backpack, you will notice they come in a wide variety of sizes. Naturally you will start wondering which is the right size backpack for you.

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While there is no perfect answer to this question, there are some general rules you can associate with the different backpack sizes. Below is a guide to give you a better idea of what backpack size you need.

Weekend (1-3 nights; 30-50 liters)

Multiday (3-5 nights; 50-80 liters)

Extended-trip (5+ nights; 70 liters or larger)

Lets look at each size a little more closely:

Weekend
These are going to be about the smallest real backpacks you can find. The smaller size packs are good for a simple overnighter and some ultralight packing. The larger sizes will hold the basics needed for about any three season hike.

Here are a few popular weekend backpacks:

Multiday
These packs get big and heavy real fast. These are good for 4 season trips as long as you pack appropriately. They will hold all the basic gear as well as some addition food storage, extra layers, and maybe even some camp luxuries like a chair or more camp kitchen gear.

Here are a few popular multiday backpacks:

Extended-trip
These bags are BIG and built to carry a lot of gear. Honestly, I don’t see a lot of single backpackers carrying packs this large. Typically I see these larger backpacks with people who are doing more than just backpacking. They are doing things like climbing or photography, things that require lots of extra gear.

Here are a few popular extended-trip backpacks:

That said, choosing the perfect pack size really depends on you and your backpacking style.

Do you want to go lightweight as possible?

Will you be backpacking with your family, friends, or by yourself?

What time of year will you mostly be backpacking?

All of these questions will have an impact on the size backpack you buy. For example, the average 3 season backpack size for a weekend trip is around 40 liters. However, if you will be doing a lot of winter backpacking, you will want a much larger size to accommodate all the bulky clothing and layers you’ll need.

If you can, before you buy your first backpack I suggest borrowing a couple different ones in a variety of sizes. This way you can test out different fits and volumes to see what works best for you. Some smaller outfitters will even rent out gear. This can be a great way to test out the different size backpacks as well.

What size backpack works for you?

Its important to remember that none of these suggestions are set in stone. They are nearly meant to give you an idea of what works for the average backpacker. For example, I use a 30 liter bag for 3-4 day trips in 3 seasons. But, thats because I have some very light gear and don’t bring much more than the 10 essentials and an extra pair of socks.

So what size backpack do you use for your trips and how did you decide on that? Has your backpack size changed as you have evolved as a backpacker or has it stayed about the same over the years?

Share your stores and advice in the comments below.

Know anyone looking at getting into backpacking and buying their first backpack? Share this post with them if you think it will be helpful!